Magnetic compounds as coatings on polymer particles and magnetic properties of the composite particles

Spherical micron-sized polymer particles coated with magnetite have been pr epared by a new method consisting of a two step process, in which iron comp ounds are coated on a micron-sized polymer core by controlled hydrolysis of FeCl3 in the presence of urea, poly(vinylpyrrolidone) and hydrochloric aci d. The thickness of the coating layer could be altered by adjusting the amo unt of FeCl3 added to the system. Magnetic particles were obtained by treat ing the coated powders with hydrogen at moderate temperatures. The chemical composition and morphology of the coating layer, and the resulting magneti c properties varied with the calcination conditions.